For Security purpose,we also have to hide SSN number or Masked
Below property will be used for masking first 5 digit of SSN as X and showing Last four digit.
public string LAST_FOUR_DIGIT_SSN
string LastFourDigitSSN = ssn.Substring(5, 4);
return "XXX-XX-" + LastFourDigitSSN;
Use it any where on the page.